1. Field of the Invention
The present invention relates to an imaging apparatus including an optical element such as an image pickup apparatus including an image pickup device that obtains an image signal corresponding to light irradiated on a photoelectric conversion surface of the image pickup device or an image projecting apparatus including a display element that displays an image to be projected on a screen and a vibrating device that vibrates a dust-proof member arranged on a front surface of the optical element in such an imaging apparatus.
2. Description of the Related Art
In recent years, quality of a generated image or a displayed image is remarkably improved in imaging apparatuses in the forms of such as an image pickup apparatus including an image pickup device and an image projecting apparatus including a display element such as liquid crystal, i.e., imaging apparatuses including optical elements such as an image pickup device and a display element. Therefore, when dust and the like adhere to the optical element arranged in a vicinity of the image pickup device or the display element, a significant problem occurs if shadows of the dust and the like are reflected on the generated image or the displayed image.
For example, in an image pickup apparatus such as a digital camera of a so-called “lens-replaceable” form configured such that a photographing optical system (a lens barrel) can be detachably attachable to an apparatus main body (a camera main body), a user can attach and detach and replace a desired photographing optical system (lens barrel) at will when the user desires. Therefore, an image pickup apparatus generally put to practical use is configured such that a plurality of kinds of photographing optical systems (lens barrels) can be selectively used for a single apparatus main body (camera main body).
In the lens-replaceable image pickup apparatus such as the digital camera of such a form, when the photographing optical system (the lens barrel) is detached from the apparatus main body (the camera main body), in some cases, dust and the like floating in an ambient environment in which the image pickup apparatus is placed intrude into an inside of the apparatus main body (the camera main body) and adhere to a surface (a light receiving surface) of the image pickup device. In other cases, dust and the like stirred up from various mechanism sections provided on the inside of the apparatus main body (the camera main body) and configured to mechanically operate, for example, various mechanism sections such as a shutter mechanism and a diaphragm mechanism during operations of the mechanism sections adhere to a surface of the image pickup device.
Likewise, in a projection type image display apparatus such as a projector configured to enlarge and project an image, which is displayed on a display element such as a CRT or liquid crystal, on a screen using a light source and a projection optical system to allow a viewer to enjoy the projected image, dust and the like sometimes adhere to a surface of the display element and shadows of the dust and the like are enlarged and projected on the screen.
In the imaging apparatuses in such forms explained above, various mechanisms for removing the dust and the like adhering to the surface of the optical element provided on the inside have been proposed.
For example, Japanese Patent Application Laid-Open Publication No. 2004-64555 discloses an electronic image pickup apparatus including a dust removing mechanism in which an annular plate-like piezoelectric element (vibration-applying member) is firmly fixed to an outer circumferential portion of a disc glass plate (a dust-proof member) and a cyclic voltage having a predetermined frequency is applied to the piezoelectric element, whereby concentric circle-like standing wave bending vibration is generated in a center of the disc glass plate to remove dust and the like adhering to the disc glass plate. Vibration generated at a predetermined excitation frequency is a standing wave having nodes in a concentric circle shape.
Supporting of the dust-proof member and dust-proof between the dust-proof member and the image pickup device are performed by a dust-proof member receiving member that is in contact with the dust-proof member in a concentric circle shape. In this case, a contact region of the dust-proof member receiving member with the dust-proof member is set to be a node of the concentric circle-like standing wave.
On the other hand, in means disclosed in Japanese Patent Application Laid-Open Publication No. 2007-267189, piezoelectric elements are respectively provided on opposed sides of a rectangular plate-like dust-proof member, the piezoelectric elements are caused to generate vibration having a predetermined frequency, and the dust-proof member is caused to resonate to set the dust-proof member in a vibration mode of a standing wave in which nodes parallel to the sides are generated. In order to remove dust and the like adhering to the nodes of the vibration, the dust-proof member is caused to resonate at different frequencies to generate a plurality of vibration modes of standing waves and change positions of the nodes. In all the vibration modes, bending vibration having nodes parallel to the sides of the dust-proof member is generated. For supporting of the dust-proof member, standing waves having different frequencies are generated such that the nodes of the vibration generally coincide with one another and vicinities of the nodes of the vibration are supported by the supporting member, whereby a vibration loss is reduced. A seal having a frame shape and a lip shape in section that prevents intrusion of dust and the like is set between an image pickup surface side and the dust-proof member.
Further, in means disclosed in Japanese Patent Application Laid-Open Publication No. 2010-239606, piezoelectric elements are respectively provided on opposed sides of a rectangular dust-proof member, the piezoelectric elements are caused to generate vibration having a predetermined frequency, and the dust-proof member is caused to resonate to generate vibration having a ridge line of a mountain of vibration surrounding a center of the dust-proof member. A pressing force of the dust-proof member at this point is set to 2 N (Newton) or less, whereby a pressing supporting structure for the dust-proof member with an extremely small vibration loss of the dust-proof member is obtained. A supporting section is provided in a member opposed to the dust-proof member. The supporting section supports nodes of vibration of the dust-proof member when an external force is simultaneously applied in a pressing direction.
Japanese Patent Application Laid-Open Publication No. 2008-228074 discloses a form in which vicinities of four corners of an optical element, which is a dust-proof member, are firmly fixed to four corners of a holding member by a conductive adhesive.